My guild members used one of the blue wash out pens for a raffle quilt. Most of the blue marks came back after washing. The quilt couldn't be raffled the blue marks never went away. They tried everything, almost faded the quilt trying. The next quilt Frixion pens were used, only the red ink ones. The Frixion marks went away after washing and drying. No iron was used. A guild member won the quilt and no marks have ever reappeared. I guess it's a gamble with the Frixion pens, always test a sample on the fabric that is exactly used in the quilt. Starched? Prewashed? and anything else done to the quilt fabric for the test.